Method of constructing gravity-type marine structure and structure by same

ABSTRACT

In case of constructing a gravity-type marine structure at a spot with a comparatively great depth of water, a footing 2 serving as a float is constructed in a dry dock, and a cylindrical body 4 constituting an underwater substructure is constructed on the footing 2 in a shallow sea yard. The cylindrical body 4 is telescopically assembled and an upper cylinder 4C is made to function as a float. Ballast water W b  is filled in the footing 2 at the installing spot with a great depth of water to submerge the footing 2, and a lower cylinder is extended with the upper cylinder 4C as a float. After the footing 2 has landed, the footing 2 and the cylindrical body 4 are charged with a filler, and an upper structure on the sea is constructed on the upper part of the cylindrical body 4. Since the cylindrical underwater substructure is constructed in the telescopic form on the footing serving as the float, a structure adapted for a sea area with a great depth of water is constructed while the stability as the float is easily kept, even in an area incapable of ensuring a quiet coastal area with a great depth of water. In the installing spot with a great depth of water, the buoyancy and gravity are utilized to easily extend the structural body without any large-scale driving apparatus, and a huge structure is easily installed in a submerged state.

SPECIFICATION

1. Technical Field

This invention relates to a gravity-type marine structure constructionmethod and a gravity-type marine structure applicable to a bent for agrand-scale sea bridge and a platform for petroleum or gas production orthe like, which are installed in a sea area with a great depth of water.

2. Background Art

Recently, demand has increased for the construction of a marinestructure installed in a sea area with a great depth of water.Structurally, the marine structures are roughly classified into agravity type, a legged type and a floating type. Among these types, thegravity type or legged type is made the basis of a bent for agrand-scale sea bridge and a platform for petroleum or gas production,since such structures are needed to be rigidly fixed on the seabed.

The present invention is particularly concerned with a marine structureof the gravity type applied as the most suitable structural type to acase where a whole structural body requires high stiffness as one ofrequired performance. In order to avoid a long-term construction on thesea in the installing spot because of risks, the gravity-type marinestructure is usually constructed according to a quick constructionmethod as follows. Namely, the major part of a structural body isconstructed on land or on a quiet coastal area, then towed in fineweather to the installing spot, and then installed in a submerged state.

More specifically, according to the conventional construction method,the structural body is constructed in a dry dock as much as possiblewithin the draft of the dry dock. The structural body thus constructedis caused to float and then towed out of the dock. Thereafter, in aquiet coastal area with a depth of water approximately equivalent tothat of the installing spot, the remaining structural body isconstructed in a floating state on the sea for a long time.

However, in the conventional construction method, when the installingspot has a great depth of water, a quiet coastal area adapted toconstruct the major part of the structural body needs the depth of waterequivalent to that of the installing spot. Therefore, in the areasatisfying these very rare natural conditions such as the northernEurope having fjord coasts, many satisfactory results have already beengiven in construction of a large-scale gravity-type marine structure.However, as for the other areas, it was impossible to find a sea areawhich has a great depth of water in a spot close to the coast andsatisfies the quiet natural conditions including waves and tidalcurrents or the like so as to ensure a long-term construction.

Consequently, the conventional gravity-type marine structure cannot beadapted for a sea area with a great depth of water except for thespecific area, resulting in the disadvantage of the conventionalgravity-type marine structure.

In various types of structures, regardless of the marine structure,various methods have already been provided to construct a structuralbody in a required form by extending or contracting the structural bodyby a driving apparatus utilizing specific energy. However, when theabove methods are applied to the construction of the marine structurefor a sea area with a great depth of water, it is necessary for themarine structure to withstand severe natural conditions (heavyhydrostatic pressure, wave power, tidal power, ice pressure, windpressure and seismic force or the like). Thus, incomparatibly greaterscale and strength to the land structures are required for the marinestructure in the sea area with a great depth of water.

Therefore, the structural body should be constructed on a huge scale inorder to withstand such severe natural conditions. A considerable amountof energy is required for expanding or contracting such a hugestructural body by a usually-used mechanical driving apparatus. Further,the size of the driving apparatus is increased. Thus, it is almostimpossible at present to apply the already-provided methods to theconstruction of the marine structure for a sea area with a great depthof water.

The present invention has been made to solve the above-mentionedproblems, and it is an object of the present invention to provide agravity-type marine structure and a method of constructing same, whichis constructed at an installing spot with a comparatively great depth ofwater even in an area incapable of ensuring a quiet coastal area with agreat depth of water, and which easily enables the extension of astructural body for installation without using a driving apparatusrequiring specific energy.

DISCLOSURE OF THE INVENTION

A construction method according to the present invention for installinga gravity-type marine structure in a sea area with a comparatively greatdepth of water comprises the steps of: constructing a hollow footing forthe gravity-type marine structure in a dry dock; constructing atelescopic underwater substructure for the gravity-type marine structureon the footing in the dry dock or a sea yard in a shallow sea area toeasily stabilize the footing as a floating body; towing the footing andthe underwater substructure to an installing spot; filling ballast waterin the footing, which is at a standstill in a floating state at theinstalling spot, to submerge the footing; thereby extending a lower partof the underwater substructure with an upper part thereof functioning asa float; and charging the footing or the underwater substructure with afiller at need after the footing has landed on the seabed.

A steel or concrete structure or a hybrid structure composed of steeland concrete is applied to a structural body of the footing and theunderwater substructure or the like. The underwater substructure may bearranged singly or in plurality. Further, the underwater substructure isconstructed in the sea yard in the shallow sea area, but it may beconstructed in the dry dock.

In case of submerging the underwater substructure in an extended state,seawater flows in the lower part of the underwater substructure.However, in case of charging the underwater substructure with thefiller, the charging may be carried out in the water. Otherwise, afterthe footing has landed on the seabed, seawater may be drained from theunderwater substructure to charge the underwater substructure with thefiller in the air.

The gravity-type marine structure according to the present inventionrelates to a gravity-type marine structure installed in a sea area witha comparatively great depth of water, and comprises a hollow footingcapable of exerting buoyancy and also capable of being filled withballast water to meet the stabilizing conditions as a floating body, andan underwater substructure constructed on the footing and composed of aplurality of cylindrical bodies assembled in a telescopic form to easilystabilize the footing as the floating body such that the cylindricalbodies other than the cylindrical body fixed to the footing are madetelescopic relatively to the cylindrical body fixed to the footing,wherein the upper cylindrical body of the underwater substructure servesas a float capable of exerting buoyancy to meet the stabilizingconditions as the floating body.

The footing is reinforced with and divided into a plurality of partsthrough partitions composed of inner slabs and bulkheads or the like.Further, the footing is provided with a plurality of intake valves totake in ballast water.

The uppermost cylindrical body of the underwater substructure serves asa float, in which a bulkhead is provided in a middle part, a lower partis submerged and a float chamber is defined in an upper part.

A connection portion between the cylindrical bodies of the underwatersubstructure is provided with hooks brought into engagement with eachother to prevent the cylindrical body from falling off in case ofextending the cylindrical body.

The lower part of each cylindrical body of the underwater substructureis provided with a water through hole permitting the communicationbetween the inside and the outside of each cylindrical body to make itpossible to naturally flow seawater in each cylindrical body.

The footing is provided with a closable filler-charging inlet to make itpossible to charge the footing with the filler. Further, the bulkhead ofthe uppermost cylindrical body of the underwater substructure isprovided with a filler-charging shaft to make it possible to charge thefiller on the sea.

Incidentally, when the underwater substructure is charged with thefiller in the air, water cut-off packings are arranged between thehooks. In this case, after the underwater substructure has beenextended, a temporary float is fixed to the upper cylindrical body.Subsequently, the cylindrical bodies are clamped together at theconnection portion to cut off seawater, and the seawater is drained fromthe underwater substructure so as to charge the underwater substructurewith the filler in the air.

In the constitution described above, in case of constructing thestructural body, the footing functions as the float, and the underwatersubstructure assembled in the telescopic form is constructed on thefooting. Therefore, the whole structural body is constructed in the drydock or the sea yard in the shallow sea area, while easily stabilizingthe footing as the floating body. As a result, it is possible toconstruct the gravity-type marine structure in the installing spot witha great depth of water, even in an area incapable of ensuring a quietsea yard in a coastal area with a great depth of water.

The footing and underwater substructure thus constructed are towed withthe footing functioning as the float to the installing spot with a greatdepth of water, and the ballast water is filled in the footing at theinstalling spot. Only by this process, the lower part of the underwatersubstructure is automatically extended with the upper part thereoffunctioning as the float, and the buoyancy and the gravity are utilizedto easily obtain huge power required for submerging. After the footinghas landed on the seabed, the footing and the underwater substructureare charged with the filler at need to ensure the stability and thestrength of the structural body. Subsequently, the upper structure onthe sea is constructed on the upper end of the uppermost cylindricalbody of the underwater substructure to attain a complete marinestructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal sectional view showing a gravity-typemarine structure as an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view showing the gravity-typemarine structure shown in FIG. 1;

FIGS. 3 to 7 are schematic sectional views showing processes of a methodof constructing a gravity-type marine structure according to the presentinvention in order, respectively;

FIG. 8 is a schematic sectional view showing the filler-charging workcarried out in the air according to the construction method;

FIG. 9 is a front view showing a gravity-type marine structure asanother embodiment of the present invention;

FIG. 10 is a plan view showing the gravity-type marine structure asanother embodiment of the present invention; and

FIG. 11 is a sectional view showing the gravity-type marine structure asanother embodiment of the present invention.

BEST MODE FOR EMBODYING THE INVENTION

Hereinafter will be given of a description of an embodiment of thepresent invention with reference to the accompanying drawings. Theillustrated embodiment relates to a gravity-type marine structuresupposed to be applied to a bent for a grand-scale sea bridge.

As shown in FIG. 1, a lower structural body of a gravity-type marinestructure 1 comprises a hollow circular footing 2 functioning as a floatand capable of being submerged by means of filling ballast water W_(b),and an underwater substructure 3 constructed on the footing 2 andincluding a three-stage circular cylindrical body 4 composed of threecylinders assembled in a telescopic form to be made telescopicrelatively to the footing 2.

As shown in FIG. 2, the footing 2 is reinforced with and divided into aplurality of ballast chambers through, for instance, an outer slab 2a,inner slabs 2b concentric with the outer slab and radial bulkheads 2cwhich are all provided in the hollow inside of the footing. Further, asshown in FIG. 1, a remote-controlled closable intake valve 5 is providedto enable each ballast chamber to take in ballast water. In submerging,the intake valve 5 adjusts the intake of water to each ballast chamberof the footing 2 and controls so as to stably submerge the entirestructural body while the relation between the center of buoyancy andthe center of gravity of the entire structural body maintains thestability as a floating body. Further, the upper slab 2a included in thefooting 2 to be located inside the cylindrical body 4 is provided with aremote-controlled closable inlet 6 to make it possible to charge theunderwater substructure with a filler.

The cylindrical body 4 includes a lower cylinder 4A having the largestdiameter, and an upper cylinder 4C designed to be the longest among thecylinders. The lower cylinder 4A is fixed to the footing 2, and a middlecylinder 4B and the lower cylinder 4C are made movable in the verticaldirection with the outer cylinder as a guide. Further, whollyflange-like or partially-projected hooks 7 are provided on the innersurfaces of the upper ends of the lower cylinder 4A and the middlecylinder 4B to prevent the cylinders from falling out. Also, hooks 8similar to the hooks 7 are provided on the outer surfaces of the lowerends of the middle cylinder 4B and the upper cylinder 4C and broughtinto engagement with the hooks 7 to prevent the cylinders from fallingout.

Furthermore, water through holes 9 are provided in the lower ends of thecylinders 4A, 4B and 4C and equipped with water intake valves permittingthe communication between the inside and the outside of the cylindersand capable of being opened or closed by the remote control. In thiscase, the intake valves are opened to make it possible to naturally flowseawater in the cylinders. The lower cylinder 4A and the middle cylinder4B serve as chambers which are communicated with the seawater to exertno buoyancy. The upper cylinder 4A has a bulkhead 10 at the middle part,which divides the upper cylinder into a lower submerged part and anupper open float chamber 11. Therefore, the upper cylinder 4A isdesigned to serve also as a float exerting the buoyancy to meet thestabilizing conditions as a floating body.

The bulkhead 10 has an opening, and an upwardly erected shaft 11 forcharging the filler is projected in the opening to make it possible tocharge the footing 2 and the extended cylinders 4A, 4B and 4C with thefiller on the sea. The filler-charging shaft 11 serves also as a shaftto transmit a vertical load at the completion at need.

In the constitution described above, the gravity-type marine structureis constructed as follows (See FIGS. 3 to 7)

(1) As shown in FIG. 3, a dry dock 20 having a depth enough to float andtow the footing in the next process is constructed in a land area closeto sea, and the footing 2 is constructed in the dry dock 20. Further,skirts and dowels or the like are installed on the bottom of the footing2 at this stage, if required in the landing on the seabed (or mound) atthe installing spot as will be described later.

(2) After the completion of the footing 2, the dry dock 20 is filledwith water to float the footing 2. Then, a gate 21 is opened to tow thefooting 2 out of the dry dock 20. The footing 2 is hereat able to exertthe buoyancy equivalent to the weight of the footing at the draft D₀.Therefore, the dry dock 20 may be designed to be deeper than the draftD₀.

(3) The footing 2 is towed to a sea yard 22 in the shallow sea area by atugboat or the like.

(4) As shown in FIG. 4, the footing 2 is firmly moored by anchors or thelike in the sea yard 22 in the shallow sea area so as to withstand along-term construction of the underwater substructure. Then, the insideupper cylinder 4A serving as a float to meet the stabilizing conditionsas the floating body is constructed. Incidentally, it is necessary forthe sea yard 22 in the shallow sea area to meet the quiet naturalconditions including waves and tidal currents.

(5) The middle cylinder 4B is constructed to surround the upper cylinder4C.

(6) The lower cylinder 4A is constructed to surround the middle cylinder4B. The sea yard 22 in the shallow sea area may have a depth of waterenough to cover the draft D₁.

(7) As shown in FIG. 5, the footing 2 mounted with the completelyconstructed cylindrical body 4 is towed to the installing spot 23, andmoored by anchors or the like on the seabed or a mound 24 preliminarilyformed at need to rest the footing in a floating state.

(8) Ballast water W_(b) is filled in the footing 2 to start submergingthe footing slowly. Then, seawater naturally flows in the lower cylinder4C, the middle cylinder 4B and the bottom of the upper cylinder 4Athrough the water through holes 9.

(9) Since seawater W_(a) continues naturally flowing in the lowercylinder 4C, the middle cylinder 4B and the bottom of the upper cylinder4A, the upper cylinder 4C gradually exerts buoyancy. In addition,ballast water W_(b) sufficient to offset the buoyancy is kept flowing inthe footing 2 to continue submerging.

(10) As shown in FIG. 6, when the submerging advances so that the draftD₃ of the upper cylinder 4C reaches a predetermined depth, the uppercylinder 4C exerts the function as the float. The upper cylinder 4Citself meets the stabilizing condition as the floating body and entersthe floating state. Since the middle cylinder and its lower partcontinue submerging, the middle cylinder 4B and its lower part areextended downward against the upper cylinder 4C. From a different pointof view, the upper cylinder 4C is extended against the middle cylinder4B.

(11) When the submerging further advances, the upper cylinder 4C and themiddle cylinder 4B are brought into engagement with each other by thehooks 7, 8. Until the buoyancy exerted on the upper cylinder 4C becomeslarger than the resultant weight of the upper cylinder 4C and the middlecylinder 4B, the submerging is continued with the entire bodyconsolidated into a unit while maintaining the current state of thecylindrical body. When the submerging advances so that the draft D₄ ofthe upper cylinder 4A reaches a predetermined depth, the upper cylinder4C starts hanging the middle cylinder 4B, and only the lower cylinder 4Aand the footing 2 continue submerging. In this case, since the lowercylinder 4A and its lower part continue submerging, the lower cylinder4A and its lower part are extended downward against the middle cylinder4B. From a different point of view, the middle cylinder 4B is extendedagainst the lower cylinder 4A.

(12) When the submerging further advances, each of the lower cylinder4A, the middle cylinder 4B and the upper cylinder 4C is extended to itsfull length.

(13) As shown in FIG. 7, when each of the lower cylinder 4A, the middlecylinder 4B and the upper cylinder 4A is extended to its full length,the ballast water W_(b) is gradually filled in the upper cylinder 4C tocause the footing 2 to land on the seabed with a predetermined depth ofwater. Thereafter, the ballast water W_(b) is additionally filled in thefooting 2 to stabilize the structural body. Incidentally, after thestructural body has landed on the seabed, grouting or the like isexecuted between the seabed (or mound) and the footing at need toprevent an excessive local contact pressure from being applied. Further,the processes (7) to (13) are to be executed in fine weather.

(14) After the structural body has landed on the seabed, the filler 13enough to satisfy the performance required at the completion is chargedinside the footing and the required parts of the cylinders 4A, 4Bthrough the inlet 6 and the shaft 12, and further charged inside therequired part of the cylinder 4C to secure the stability and strength ofthe structural body required at the completion. Subsequently, an upperstructure 30 on the sea is constructed to attain a complete marinestructure.

The above embodiment is applied to a case where the structural body ischarged with the filler in the water. However, the structural body maybe charged with the filler in the air. In this case, as shown in FIG.8(A), water cutoff packings 14 are attached, for instance, on the lowersurfaces of the upper hooks 7 (wholly flange-like hooks) of the middlecylinder 4C and the lower cylinder 4A. Then, the water cutoff packings14 are activated between the hooks 7, 8 to make it possible to maintainthe airtightness in the foregoing process (14), as shown in FIG. 8(B).

In the construction in the air, the movement of each member in theprocesses (1) to (13) is similar to that in the underwater construction.However, the process (14) in the construction in the air is executed asfollows (See FIG. 8(B)).

(14-1) After the structural body has landed on the seabed, the temporaryfloat 15 is installed to the upper periphery of the upper cylinder 4A,and connected to the upper end of the upper cylinder 4A through, forinstance, a wire rope or the like. This process is to supplement thebuoyancy, since the buoyancy exerted on the upper cylinder 4A is lostwhen seawater is drained from the cylindrical body 4 in the subsequentprocess. Further, the buoyancy exerted by this temporary float 15 is setto be as large as the buoyancy which is enough to hold the uppercylinder 4A and the middle cylinder 4B and enables the water cutoffpackings 14 to exert the water cutoff function.

(14-2) The footing is charged with the filler in a predetermined manner.

(14-3) The valve of the water through hole 9 in the lower part of thelower cylinder 4A is closed. Since the water through holes 9 of theother cylinders do not face the outside, these water through holes 9 arekept unchanged.

(14-4) The seawater is drained from the cylindrical body 4 by anappropriate means.

(14-5) The cylindrical body 4 is charged with the filler in the air.This charging work is carried out until the structural body of thecylindrical body portion including the connection parts between thecylinders satisfy the function required at the completion.

(14-6) Subsequently, the predetermined upper structure 30 is constructedfor completion.

FIGS. 9 to 11 show a gravity-type marine structure as another embodimentof the present invention, respectively. According to this embodiment, apair of underwater substructures 3 composed of the cylindrical bodies 4are installed on the left and right sides of a circular footing 2 inplane. Then, the upper parts of each cylindrical body 4 are connectedtogether by reinforcing members 16, and the upper ends of the pair ofcylindrical bodies 4 are connected together by the upper structure 30 onthe sea.

In the above embodiments, the planar shape of the footing 2 is circular.However, the footing 2 may take a rectangular, polygonal or any otherdesired shape. Further, the underwater substructure 3 may be arrangedplanarly on the footing singly or in plurality at will. Furthermore, thecylindrical body may take a circular, rectangular, polygonal or anyother desired shape at will.

Moreover, it is possible to impose the float function on the middlecylinder 4B. The cylindrical body is extended in three stages in theabove embodiment. However, a two-stage cylindrical body without themiddle cylinder or a multi-stage cylindrical body in four or more stagesfalls within the true spirit and scope of the present constructionmethod.

In the above embodiments, it is assumed that the construction method isapplied to the bent for a grand-scale sea bridge. However, it is amatter of course that the present invention is applied to otherlarge-scale gravity-type marine structures.

INDUSTRIAL APPLICABILITY

The construction method of the present invention comprises the steps ofconstructing a multi-stage cylindrical body, which constitutes theunderwater substructure, on the footing serving also as a float in thesea yard in the shallow sea area, then submerging the footing at theinstalling spot with a great depth of water, thereby extending the lowercylinder with the upper cylinder functioning as the float, and theninstalling the footing in a landing state. Therefore, the presentinvention is applicable to the following.

(1) It is possible to construct a gravity-type marine structure adaptedfor a sea area with a great depth of water, even in an area incapable ofensuring a quiet coastal area with a depth of water equivalent to thatof the installation spot with a great depth of water.

(2) It is possible to produce huge power to extend the structural bodyby utilizing the buoyancy by seawater and the gravity, and the hugegravity-type marine structure is easily installed even in a sea areawith a great depth of water without using a large-scale drivingapparatus.

We claim:
 1. A method of constructing a gravity-type marine structure incase of installing the gravity-type marine structure in a sea area witha comparatively great depth of water, comprising the stepsof:constructing a hollow footing for the gravity-type marine structurein a dry dock, the footing exerting buoyance in water to function as afloat and having an intake valve capable of taking in ballast water;constructing a telescopic underwater substructure having at least anupper cylindrical body and a lower cylindrical body for the gravity-typemarine structure on the footing in the dry dock or a sea yard in ashallow sea area to easily stabilize the footing as a floating body, theupper cylindrical body of the underwater substructure having a bulkheadin the middle part to exert buoyance so as to function as a float, andeach cylindrical body of the underwater substructure having a waterthrough hole permitting the water communication between the inside andthe outside of the cylindrical body; towing the footing and theunderwater substructure to an installing spot; filling ballast water inthe footing through the intake valve, which is at a standstill in afloating state at the installing spot, to submerge the footing; thenextending the lower cylindrical body of the underwater substructure withthe submerge of the footing while the upper cylindrical body thereoffunctioning as the float; and landing the footing on the seabed.
 2. Amethod of constructing a gravity-type marine structure in case ofinstalling the gravity-type marine structure in a sea area with acomparatively great depth of water, comprising the steps of:constructinga hollow footing for the gravity-type marine structure in a dry dock,the footing functioning as a float and having an intake valve capable oftaking ballast water therethrough; constructing a telescopic underwatersubstructure having at least an upper cylindrical body and a lowercylindrical body for the gravity-type marine structure on the footing inthe dry dock or a sea yard in a shallow sea area to easily stabilize thefooting as a floating body, the upper cylindrical body of the underwatersubstructure having a bulkhead in the middle part to function as afloat, and each cylindrical body of the underwater substructure having awater through hole permitting the water communication between the insideand the outside of the cylindrical body; towing the footing and theunderwater substructure to an installing spot; filling ballast water inthe footing through the intake valve, which is at a standstill in afloating state at the installing spot, to submerge the footing;extending the lower cylindrical body of the underwater substructure withthe submerge of the footing while the upper cylindrical body thereoffunctioning as the float; and charging the footing or the underwatersubstructure with a filler, after the footing has landed on the seabed.3. A method of constructing a gravity-type marine structure according toclaim 2, wherein the underwater substructure is charged with the fillerin the water.
 4. A method of constructing a gravity-type marinestructure according to claim 2, wherein after the footing has landed onthe seabed, seawater is drained from the underwater substructure, andthe underwater substructure is charged with the filler.
 5. Agravity-type marine structure installed in a sea area with acomparatively great depth of water, comprising:a hollow footing capableof exerting buoyancy to function as a float, the footing having anintake valve capable of taking ballast water therethrough; and anunderwater substructure constructed on the footing and composed of aplurality of cylindrical bodies assembled in a telescopic form such thatcylindrical bodies other than the lowermost cylindrical body fixed tothe footing are made telescopic relatively to the lowermost cylindricalbody; wherein the upper cylindrical body of said underwater substructureserves as a float capable of exerting buoyancy by having a bulkhead inthe middle part thereof, and each cylindrical body of the underwatersubstructure having a water through hole permitting the communicationbetween the inside and the outside of the cylindrical body.
 6. Agravity-type marine structure according to claim 5, wherein the footingis divided into a plurality of parts through inner partitions.
 7. Agravity-type marine structure according to claim 5 or 6, wherein theconnection part between the cylindrical bodies of the underwatersubstructure has hooks brought into engagement with each other.
 8. Agravity-type marine structure according to claim 5 or 6, wherein thefooting has a closable inlet enabling the charging of the filler.
 9. Agravity-type marine structure according to claim 5 or 6, wherein theuppermost cylindrical body of the underwater substructure has a shaftenabling the charging of the filler.
 10. A gravity-type marine structureaccording to claim 7, wherein water cutoff packings are able to bearranged between the hooks.